Technique / Discuss

murburger01    says:

it depends on the image you have that you want to resize...
more info?
Posted 3 months ago. ( permalink )

chadmiller    says:

Only resize where you don't chop pixels in parts. There is no other way.
Posted 3 months ago. ( permalink )

rafasgj says:

The sharpening should be the last step in the post-processing workflow.

After a resize, apply a sharpen to the image.
Posted 3 months ago. ( permalink )

Eyal Soudry says:

murburger01, why is it depend on the image i want to resize?
chadmill, i didn't understand your point...
rafasgi, good idea, thanks
Posted 3 months ago. ( permalink )

murburger01    says:

what I mean is what sort of size image is it that you want to resize 2mp 3mp to what? I remember reading somewhere that 25% is the limit.
Posted 3 months ago. ( permalink )

rafasgj says:

Any resize will require interpolation and will somewhat change the sharpness of the image, be it to a bigger or smaller size. Often, the "samller" image is "acceptable" so we don't apply sharpen aftwards (but most would benefit from some sharpening).

I have resized images up to 100% with good results using only "standard" tools. I believe a 200% would be feasible depending on the image.

If you need/like/want, bigger enlargements can be done with specialized software like Genuine Fractals (google/yahoo it). I once tested it to resize an image by 500% and the results were amazing (not without loss of quality, but much less than expected).
Posted 3 months ago. ( permalink )

Chris_Malcolm    says:

Some resizing methods are much better than others. Among the better ones are bicubic interpolation, Lanczos, and whatever Genuine Fractals does. I would be suspicious of any kind of resizing which did not advertise what kind of method it was based on. There are some cheap and nasty methods around, including surprisingly enough in some expensive image editors. Good downwards resizing should always improve sharpness. Good resizing upwards should lose less sharpness than you'd expect for the amount of magnification.

Irfanview, which is available free, offers several methods of resizing, including Lanczos, so you can do some comparisons.
Posted 3 months ago. ( permalink )

Paul Vernon Photography    says:

Most alterations to an image, reduce sharpness. It's part of the voodoo.

Do all of your image adjustments (except sizing) at the maximum resolution you can get. Save that file, preferably as a PSD with all layers intact.

Then, for each and every size of print or web display: flatten the PSD, resize the image, and LASTLY sharpen the image as appropriate. Best practice is then to save the image as a TIF with the size included somewhere in the filename. You end up with a lot of files, but they are all the best you can make them be.
Posted 3 months ago. ( permalink )

Vieira    says:

rafasgj wrote

I have resized images up to 100% with good results

rafasgj says:

Maybe I should've said that I "doubled the image size by doubling the number of pixels in one side and keeping the aspect ratio by upsizing the other dimension" or something like that?

Anyway you can't "resize" it to 100% with no quality loss. You can "display it" to 100%, what would give a resize of exactly 0%.
Posted 3 months ago. ( permalink )

Eyal Soudry says:

thank you all.
I'll look for Genuine Fractals and test the results
Posted 3 months ago. ( permalink )

Mark_Twells    says:

Think of the number of pixels as the amount of information in an image. If you shrink the image, you cut down the amount of information in it. In English, it won't be as detailed - as sharp.

It follows that if you interpolate an image you have downsized you can't invent the extra information you need to make it as good as the original.
Originally posted 3 months ago. ( permalink )
Mark_Twells edited this topic 3 months ago.

El Endemoniau says:

I hope it can help. Here's an example of what i do whit PS when resize and try to enhance sharpness.
original image size 2448x3264

resized 600x800

1)Duplicate background layer.
2)With duplicated layer selected go Apply Filter/Other/High Pass.
3)Play with blend modes from Overlay to Ping Light (o whatever you like).

I used Vivid Light just to show the result.


Posted 2 months ago. ( permalink )